1. Field of the Description
The present description relates, in general, to methods and systems for providing localization or a three-dimensional coordinate in a space for an object, and, more particularly, to methods and systems for providing localization or existing spatial positions (or absolute positions) for an object in a space such as for use in accurately controlling movement of an unmanned aerial vehicle (UAV) as it flies within a space to perform a task or a land vehicle or other mobile device as it moves in a space, e.g., move UAVs in an aerial display or entertainment setting relative to set pieces and props and relative to other UAVs in the same space.
2. Relevant Background.
There is a growing interest in utilizing unmanned aerial vehicles (UAVs) such as remotely controlled drones/airplanes, helicopters, and multicopters to perform a wide variety of tasks. An exemplary UAV that is receiving growing attention is the multirotor or multicopter. This UAV is a rotorcraft with more than two rotors, and multicopters often use fixed-pitch blades with control of vehicle motion being achieved by varying the relative speed of each rotor to change the thrust and torque produced by each rotor. Multicopters may also be named quadcopters, hexacopters, and octocopters to refer to their number of rotors (e.g., 4, 6, or 8, respectively).
Due to their ease of both construction and control, multirotor aircraft are frequently used in model and radio control aircraft projects such as to provide a lower budget option for creating aerial displays (e.g., for entertainment) or for collecting aerial videos. In these implementations, the UAVs may carry a payload, such as lights, props, and/or one or more cameras, and be remotely controlled to move over a targeted object or geographical area. Electronically controlled multicopters may be powered using a battery driving brushless motors and propellers with control provided with an onboard flight controller/stabilization board selectively throttling the motors in response to control signals and that may be in communication with an operator (e.g., on the ground) using a radio controller unit. In other implementations, mobile objects such as remotely controlled land vehicles or robots may be used to perform a particular task in a space.
An ongoing challenge, though, is how to better control the UAVs and other mobile devices (e.g., mobile land or air vehicles) for particular uses or while performing differing tasks. For example, control over a mobile vehicle may require that an absolute position (or localization data) be determined for the mobile device within a space. However, it has proven problematic for a number of reasons to obtain such position information for mobile devices using onboard or off-board systems. First, localization needs to be done fast especially when the position location in the space is used for controlling the vehicle in real time. Second, with regard to onboard systems, the systems used to perform the localization often need to be very lightweight such as when they are provided on an aerial vehicle or other mobile device with a limited payload capacity. Third, again with regard to onboard systems, the localization systems need to be designed to consume relatively low amounts of power so as not to drain an onboard battery. Fourth, localization processes preferably are robust with regard to interference, distortion of observations, and system degradation (e.g., such as dirt on the mobile device or on a marker or other feature used in the localization or operating in a sensor shadow).
Off-board systems that are designed to locate a mobile device in a space typically do not have the same power and weight constraints. However, off-board systems are not useful in many applications. Particularly, onboard localization is often preferred to avoid the communications delay that occurs with off-board systems between ground (or off-board) devices and the mobile device. Further, communications between a mobile device and a remote/off-board localization system may be lost, and this would result in an unacceptable loss of localization services needed for proper control (which may force a mobile device to pause operations until communications are restored or force landing (or at least a period of hovering) for a flying vehicle).
Hence, there remains a need for methods and systems for providing localization for mobile devices such as UAVs flying within an air space or land vehicles/robot over some platform or terrain. Preferably, such localization methods and systems would provide absolute position data in a quick and efficient manner useful in real time control of movements of a mobile device.